1. Field of the Invention
The present invention pertains to a method and apparatus for anchoring casing and/or other tubular goods within a well. More particularly, the present invention pertains to a method and apparatus for anchoring casing in a well during cementing or other pumping operations, while permitting rotation of such anchored casing.
2. Brief Description of the Prior Art
Drilling of an oil or gas well is frequently accomplished using a surface drilling rig and tubular pipe. When installing pipe (or other tubular goods) into a wellbore, such pipe is typically inserted into said wellbore in a number of sections of substantially equal length commonly referred to as “joints”. As the pipe penetrates deeper into a wellbore, additional joints of pipe can be added to the ever lengthening pipe “string” at a drilling rig or other surface facility. As such, a typical pipe string comprises a plurality of interconnected sections or joints of pipe having an internal, longitudinally extending bore.
After a wellbore is drilled to a desired depth, relatively large diameter pipe known as casing is typically installed within the wellbore and cemented in place. Cementing is usually performed by pumping a predetermined volume of cement slurry into the well from the surface using high-pressure pumps. The cement slurry is typically pumped down the inner bore of the casing string, out the distal or bottom end of the casing, and back up around the outer surface of the casing. In this manner, the cement slurry leaves the inner bore of the casing and enters the annular space existing between the outer surface of the casing and the inner surface of the wellbore. The cement is allowed to harden, forming a sheath around the outer surface of the casing; this cement sheath beneficially secures the casing in place and forms a seal to prevent fluid flow along the outer surface of the casing string.
Top drive systems are commonly utilized on many drilling rigs to pick up sections of pipe within a derrick, join such pipe together (using threaded connections) and provide torque to such pipe as part of the well drilling process. More recently, such top drive systems have also been used to install casing within wellbores. In this regard, such top drive systems are frequently used in conjunction with so-called casing running tools (“RT's”), which permit casing to be reciprocated and/or rotated during casing installation and cementing operations, thereby generally resulting in better overall cementing performance.
During casing cementing operations, a cement head is typically utilized to provide a connection or interface between a top drive or RT, and a casing string that extends into a well bore. Such cement heads should beneficially permit cement slurry to flow from a pumping assembly into a well, and should have sufficient flow capacity to permit high pressure pumping of large volumes of cement and other fluids at high flow rates.
Darts, balls, plugs and/or other objects, typically constructed of rubber, plastic or other material, are frequently pumped into a well in connection with cementing operations. In many instances, such items are suspended within a cement head until the objects are released or “launched” at desired points during the cement pumping process. Once released, such items join the cement slurry flow and can be pumped down hole directly into a well. Such darts, balls, plugs and/or other objects should be beneficially held in place within the slurry flow passing through the cement head prior to being launched or released without being damaged or washed away by such slurry flow.
During casing installation operations, and especially during cement pumping operations, casing can be forced in an axially upward direction. Buoyancy forces of cement slurry, as well as pumping forces, can all act on a casing string in a well, overcoming the weight of the casing string and driving such casing string in an axially upward direction. Such upward movement by a casing string can create a number of problems including, without limitation, poor cement placement and/or bonding between the outer surface of a casing string and the inner surface of a wellbore. Such upward movement can also lead to the creation of channels and/or so-called “micro-annuluses” between casing and a cement sheath.
It is common practice to attempt to anchor casing against axial movement by connecting such casing to a blowout preventer assembly, rig structure or other secure anchor point(s) using chains, cables or other similar attachment means. However, such practice can create undesirable safety risks for personnel who must manipulate and connect such chains, cables and/or other attachment means to a casing string or attached components, frequently when there are no convenient or effective attachment points on said casing and/or related components. Moreover, such conventional attachment means often cannot be securely connected and are at risk of slipping or becoming disconnected when subjected to loading. Importantly, once casing is anchored in place, such conventional anchoring means prevent rotation of such casing, thereby negating important benefits flowing from the ability to rotate the casing.
Thus, there is a need for a means for conveniently and efficiently anchoring casing in place (including, without limitation, large diameter and heavy surface casing) during casing installation and cementing operations to offset upward forces acting on said casing. Further, such anchoring means should permit such casing to be rotated during the cementing process, and should not impede the launching of darts, balls, plugs and/or other objects.